Tuesday, January 3, 2012

Sunny-Stormy New year

The asymmetrical bell-curve is caused by having a North-South
roof ridge, and by having Sharp Hill to the SouthEast.
The white line under the Sunbox is sunlight
reflecting off the underside of the box
3 Jan 2012: Today, the UK is straddled with stormy weather http://www.bbc.co.uk/news/uk-16390088 with patches of sunshine alternating with driving rain and squalls, and a lot of structural damage further north in Scotland. But the 2 Jan 2012 could not have been better for a winter bank holiday, sunny all day! This PV score of 4.02 kWh for the day was the best since 9th December, and there is a pleasing symmetry, as they are both 11-12 days either side of the Solstice. The Sunbox scored 9.0 kWh on both those days.

Solar Angle and Sun Seeker
  The roof ridge is North-South with a 10º azimuth-swivel to south, so our solar midday (sun running axially down the ridge) is 1240. The photo of the Sunbox is taken at 1240 when there is zero shadow either side. The solar altitude at midday solstice is 13.65º, and ten days after the solstice, it's clear from the bright white line of reflected light under the Sunbox that the solar angle at the highest point is still below the leading front edge, i.e. less than 20º (it is 14.65º). It will be 2nd Feb when the highest solar angle is 20º, and after that there will by more of the day when the inclined front face of the Sunbox is incident to the solar angle.
   Info on angles comes from the iPhone App called Sun Seeker, nothing to do with posh motor yachts. As you turn it, the iPhone always knows which way to point to the Sun, even during the night. I discovered, while researching for this posting, that the App has detailed functions that I hadn't been aware of before.

Left: Solar altitude each day
Centre: The house was photographed in Summer 2007
Right: The sun path is shown in a circular chart

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